Mormonized version of the colloquial profane statement: "Mother F'er" or "Mother Fucker".
Logically followed more archaic statement "Mother of Cheese" which is, in fact, a cow, or a "mother of a heifer".

random guy on college campus: "Dude, did you just see that hot girl go by on her Razor scooter? She totally just biffed it."
random hot girl on scooter: "MOTHER HEIFER!"